ardupilot/libraries/AC_PID/AC_PI_2D.cpp

169 lines
4.3 KiB
C++

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/// @file AC_PI_2D.cpp
/// @brief Generic PID algorithm
#include <AP_Math.h>
#include "AC_PI_2D.h"
const AP_Param::GroupInfo AC_PI_2D::var_info[] PROGMEM = {
// @Param: P
// @DisplayName: PID Proportional Gain
// @Description: P Gain which produces an output value that is proportional to the current error value
AP_GROUPINFO("P", 0, AC_PI_2D, _kp, 0),
// @Param: I
// @DisplayName: PID Integral Gain
// @Description: I Gain which produces an output that is proportional to both the magnitude and the duration of the error
AP_GROUPINFO("I", 1, AC_PI_2D, _ki, 0),
// @Param: IMAX
// @DisplayName: PID Integral Maximum
// @Description: The maximum/minimum value that the I term can output
AP_GROUPINFO("IMAX", 2, AC_PI_2D, _imax, 0),
// @Param: FILT_HZ
// @DisplayName: PID Input filter frequency in Hz
// @Description: Input filter frequency in Hz
// @Unit: Hz
AP_GROUPINFO("FILT_HZ", 3, AC_PI_2D, _filt_hz, AC_PI_2D_FILT_HZ_DEFAULT),
AP_GROUPEND
};
// Constructor
AC_PI_2D::AC_PI_2D(float initial_p, float initial_i, float initial_imax, float initial_filt_hz, float dt) :
_dt(dt)
{
// load parameter values from eeprom
AP_Param::setup_object_defaults(this, var_info);
_kp = initial_p;
_ki = initial_i;
_imax = fabs(initial_imax);
filt_hz(initial_filt_hz);
// reset input filter to first value received
_flags._reset_filter = true;
}
// set_dt - set time step in seconds
void AC_PI_2D::set_dt(float dt)
{
// set dt and calculate the input filter alpha
_dt = dt;
calc_filt_alpha();
}
// filt_hz - set input filter hz
void AC_PI_2D::filt_hz(float hz)
{
_filt_hz.set(fabs(hz));
// sanity check _filt_hz
_filt_hz = max(_filt_hz, AC_PI_2D_FILT_HZ_MIN);
// calculate the input filter alpha
calc_filt_alpha();
}
// set_input - set input to PID controller
// input is filtered before the PID controllers are run
// this should be called before any other calls to get_p, get_i or get_d
void AC_PI_2D::set_input(const Vector2f &input)
{
// reset input filter to value received
if (_flags._reset_filter) {
_flags._reset_filter = false;
_input = input;
}
// update filter and calculate derivative
Vector2f input_filt_change = (input - _input) * _filt_alpha;
_input = _input + input_filt_change;
}
Vector2f AC_PI_2D::get_p() const
{
return (_input * _kp);
}
Vector2f AC_PI_2D::get_i()
{
if((_ki != 0.0f) && (_dt != 0.0f)) {
_integrator += (_input * _ki) * _dt;
float integrator_length = _integrator.length();
if ((integrator_length > _imax) && (integrator_length > 0)) {
_integrator *= (_imax / integrator_length);
}
return _integrator;
}
return Vector2f(0,0);
}
// get_i_shrink - get_i but do not allow integrator to grow in length (it may shrink)
Vector2f AC_PI_2D::get_i_shrink()
{
if((_ki != 0.0f) && (_dt != 0.0f)) {
float integrator_length_orig = min(_integrator.length(),_imax);
_integrator += (_input * _ki) * _dt;
float integrator_length_new = _integrator.length();
if ((integrator_length_new > integrator_length_orig) && (integrator_length_new > 0)) {
_integrator *= (integrator_length_orig / integrator_length_new);
}
return _integrator;
}
return Vector2f(0,0);
}
Vector2f AC_PI_2D::get_pi()
{
return get_p() + get_i();
}
void AC_PI_2D::reset_I()
{
_integrator.zero();
}
void AC_PI_2D::load_gains()
{
_kp.load();
_ki.load();
_imax.load();
_imax = fabs(_imax);
_filt_hz.load();
// calculate the input filter alpha
calc_filt_alpha();
}
// save_gains - save gains to eeprom
void AC_PI_2D::save_gains()
{
_kp.save();
_ki.save();
_imax.save();
_filt_hz.save();
}
/// Overload the function call operator to permit easy initialisation
void AC_PI_2D::operator() (float p, float i, float imaxval, float input_filt_hz, float dt)
{
_kp = p;
_ki = i;
_imax = fabs(imaxval);
_filt_hz = input_filt_hz;
_dt = dt;
// calculate the input filter alpha
calc_filt_alpha();
}
// calc_filt_alpha - recalculate the input filter alpha
void AC_PI_2D::calc_filt_alpha()
{
// calculate alpha
float rc = 1/(2*PI*_filt_hz);
_filt_alpha = _dt / (_dt + rc);
}